As is known, the essential components of a vehicle HVAC system include an air inlet, a filter for removing dust and dirt particles from the intake air, a blower, a heat exchanger unit which may include at least one of an evaporator through which flows the refrigerant of a refrigeration circuit and a radiator through which flows a heated liquid (usually that circulating in the engine cooling system), and air vents for discharging air into the cab after it has been filtered and blown through the heat exchanger unit by the blower.
The design and location of the HVAC system of an off-highway vehicle, requires careful consideration on account of the limited space available within the cab. Because off-highway vehicles often operate in a dirty environment, it is preferable for the air intake to be located at rooftop level and a compact configuration that is sometimes adopted is to place all the components of the HVAC system in a roof mounted unit. However, this is sometimes not possible, for example if the cab has an opening roof or if the HVAC unit would restrict visibility unacceptably.
An alternative solution that has been proposed is to place the blower and the heat exchanger unit beneath the seat of the operator but that too is not always practicable.
In particular, in some vehicles the clearance between the seat and the floor of the cab is not large enough to accommodate the heat exchanger unit and the blower. Furthermore, in such a configuration the air in the duct may be heated while flowing from the heat exchanger unit to vents in the console unit or dashboard.
Another solution would be to have the HVAC located partly within the cabin and partly in the engine bay but this would expose the components of the HVAC system to a dirt environment and to higher temperatures and would take up valuable packaging space within the engine bay.